68 HOW CROPS GROW. 



two molecules of dextrose, C12H22O11 -|- H2O = 2 CeHijOe. 

 Maltose is also produced when starch and dextrin are 

 heated with dilute acids, and thus appears to be an inter- 

 mediate stage of their transformation into dextrose. 



Maltose is accordingly an ingredient of some commer- 

 cial "grape-sugars" made from starch by boiling with 

 diluted sulphuric acid. 



Lactose, or Milk Sugar, C12H22O11 -|- HjO, is the 

 sweet principle of the milk of animals. It is prepared 

 for commerce by evaporating whey (milk from which 

 casein and fat have been separated for making cheese). 

 In a state of purity it forms transparent, colorless crys- 

 tals, which crackle under the teeth, and are but slightly 

 sweet to the taste. When dissolved to saturation in 

 water, it forms a sweet but thin syrup. Heated to 290° 

 the crystals become water-free. 



Lactose is said to occur with cane-sugar in the sapo- 

 dilla (fruit of Achras sapota) of tropical countries. 

 Treatment with dilute sulphuric acid converts it into 

 galactose and dextrose. 



C12H22OH + HjO = C5H,20|5 + CsHijGo 

 Lactose. Water. Galactose. Dextrose, 



Raffinose, CisHsaOis + 5 HjO (?), first discovered 

 by Loiseau in beet-sugar molasses, was afterwards found 

 by Berthelot in eucalyptus manna, by Lippmann in beet- 

 root, and by Boehm & Eitthausen in cotton-seed. It 

 crystallizes in fine needles, and is but slightly sweet. It 

 begins to melt at 190° with loss of crystal- water, which 

 may be completely expelled at 212°. The anhydrous 

 sugar fuses at 236°. It is more soluble in water and has 

 higher dextrorotatory power than cane-sugar. Heated 

 with dilute acids it yields dextrose, levulose and galactose. 



CisHsjOij + 2 H2O = 3 (C„H,20„). 



The Sugars in Bread- Grains. — The older observers 

 assumed the presence of dextrose in the bread-grains. 



